A film antenna as an in-vehicle antenna mounted on a vehicle is disclosed in JP-B2-4064978 corresponding to US Patent Application Publication No. 2005/0264461. The film antenna is arranged on and attached to a wind shield glass of the vehicle near a corner, at which a roof of a body and a pillar cross. Further, a technique for increasing a gain of an antenna having double loop shape is disclosed in JP-A-2008-113407. In the technique, a reflection element is arranged on a rear side of the antenna element.
The film antenna can be attached to a predetermined position of the windshield, which does not hinder front vision of a driver of the vehicle. Thus, the vision of the driver in front of the vehicle is secured. However, in this case, the film antenna transmits an electro-magnetic wave not only toward an outside of a compartment of the vehicle but also toward an inside of the compartment. Thus, when a communication device is disposed in the compartment, and the communication device uses the same communication frequency zone as the film antenna, the electro-magnetic wave from the film antenna may affect operation of the communication device. When the antenna having a double loop shape is mounted on the vehicle, it is necessary to secure a distance between the antenna and a body of the vehicle. Accordingly, when the antenna having a double loop shape is arranged on the windshield of the vehicle, it is difficult to secure the front vision of the driver.